1. Field of the Invention
The present invention pertains to improved methods for manufacturing the renewable energy source fuel commonly known as biodiesel.
2. Description of Related Art
Biodiesel is a mixture of fatty acid alkyl esters produced, ordinarily, from a plant source. Typically a mixture of methyl or ethyl esters is produced from a transesterification reaction involving triglyceride esters, vegetable oil and an alcohol, ordinarily methanol or ethanol, which yield glycerol as a by-product. (When the reaction involves free fatty acids specifically, it is an esterification rather than a transesterification, as those skilled in the art understand.) The methyl and ethyl esters are similar to petroleum diesel in structure and properties as fuels, which makes biodiesel suitable for routine use in present-day diesel engines.
There are various reasons further to develop biodiesel as a commercial fuel source. Interest in renewable energy resources increases every year. One reason pertains to inexorable fossil fuel reserve depletion; another is the environmental concern of fossil fuel carbon dioxide emissions and their notorious greenhouse effects. National security is also a consideration in fuels development, because even in the absence of fossil fuel reserve depletion there are severe geopolitical constraints on fossil fuel markets. Biodiesel as a fuel initiative can revitalize agriculture as an industry and even create new agricultural specialties. For example, a new agricultural specialty would be marine agriculture devoted to biodiesel production, in which oil from salt-water algae creates entire new economies and job opportunities. Also important are the environmental benefits of recycling, and used vegetable oil is a much-underused recyclable commodity in the United States today. Among the many renewable alternative energy options currently available, biodiesel has the potential to enable a smooth transition to new fuel sources because present day diesel engines require no modification in order to burn biodiesel. In fact, when Rudolf Diesel invented the diesel engine he designed it to burn peanut oil, not a fossil fuel. As fossil based fuel prices rise in contrast with the reduction of biodiesel prices over time, the commercial viability of biodiesel becomes more real every day, particularly because diesel yields almost twice the mileage per gallon as gasoline does.
Although biodiesel is being produced currently using liquid catalysts, separation issues are a challenge due to the solubility of such liquid catalysts. Separation issues which are a nuisance at a pilot batch level can create significant obstacles at scaled-up, commercial production levels. In traditional biodiesel manufacturing methods, liquid catalyst is retained in both the biodiesel and glycerol phases of the reaction product, although most of the soluble catalyst is dissolved in the glycerol phase. The traditional way to remove the catalyst was to precipitate it as a salt using an acid, which was energy intensive, and then the regeneration of the salted catalyst was cost prohibitive. Accordingly, a need remains for biodiesel manufacturing methods which rely predominantly or solely on solid catalysts, to overcome the separation issue which is a major manufacturing challenge in biodiesel production today.